The present invention is directed to a multiple-pulley accessory drive system for an automobile; and more specifically, to an accessory drive belt for such an accessory drive system.
The present invention was specifically developed to address the need for an accessory drive belt capable of relatively easy installation by stretching the drive belt over the pulleys of the multiple-pulley accessory drive system, where this drive belt maintains sufficient tension throughout the design life of the drive system.
The present invention provides a low modulus drive belt for an automotive, multiple-pulley accessory drive system that allows for relatively high elongation during installation and that maintains a relatively high percentage of its install tension throughout the useful life of the belt. The present invention also provides an automotive, multiple-pulley accessory drive system that utilizes such a belt and provides a method for constructing such a belt.
A first aspect of the present invention is directed to a multiple-pulley accessory drive system for an automobile that comprises: (a) a drive pulley; (b) an accessory pulley operatively coupled to an accessory drive shaft; and (c) an endless drive belt engaged between the drive pulley and the accessory pulley, where the drive belt includes an endless band of rubber composite material having a plurality of circumferentially extending an axially aligned polyamide 6.6 twisted cords formed therewithin. In a more detailed embodiment of this aspect of the invention, the circumferential length of the endless drive belt, before installation of the pulleys, is approximately 2% to approximately 3% lower than the nominal drive length of the accessory drive system. In a further detailed embodiment, the circumferential length of the endless drive belt, before installation on the pulleys, is approximately 2% to approximately 2.3% lower than the nominal drive length of the accessory drive system. In yet a further detailed embodiment, the axial distance between the distant cords is approximately 0.3 mm (0.012 in.) to approximately 0.4 mm (0.016 in.). In yet a further detailed embodiment, each twisted cord includes a pair of yarn strands twisted together. In yet a further detailed embodiment, each cord has diameter of approximately 0.58 mm (0.023 in.).
In an alternative detailed embodiment of the first aspect of the present invention, the endless drive belt has a tensile modulus of approximately 7000 N/mm/mm (1575 lbf/in/in) to approximately 10,000 N/mm/mm (10,000 lbf/in/in); and in an even more detailed embodiment, the endless drive belt has a tensile modulus of approximately 7800 N/mm/mm (1750 lbf/in/in) to approximately 8,500 N/mm/mm (1910 lbf/in/in). In yet a further detailed embodiment, the circumferential length of the endless drive belt, before installation on the pulleys, is approximately 2% to approximately 3% lower than the nominal drive length of the accessory drive system.
In another alternative embodiment to the first aspect of the present invention, the operational torque of the accessory drive system is less than, or equal to approximatley 2.7 N-m (2 ft-lb). In a further detailed embodiment, the accessory is an automotive water pump, and the accessory pulley is operatively coupled to a drive shaft of the water pump.
It is a second aspect of the present invention to provide a multiple-pulley accessory drive system for an automobile that includes: (a) a drive pulley; (b) an accessory pulley operatively coupled to an accessory drive shaft; (c) an endless drive belt engaged between the drive pulley and the accessory pulley, where the drive belt includes an endless band of rubber composite material having a plurality of circumferentially extending and axially aligned cords formed therewithin; (d) where the endless drive belt has a tensile modulus of approximately 7,000 N/mm/mm (1575 lbf/in/in) to approximately 10,000 N/mm/mm (2250 lbf/in/in). In a further detailed embodiment, the circumferential length of the endless drive belt, before installation on the pulleys, is approximately 2% to approximately 3% lower than the nominal drive length of the accessory drive system. In yet a further detailed embodiment, the circumferential length of the endless drive belt, before installation on the pulleys, is approximately 2% to approximately 2.3% than the lower nominal drive length of the accessory drive system. In yet a further detailed embodiment, the cords are polyamide twisted cords.
In an alternate detailed embodiment of the second aspect of the present invention the operational torque of the accessory drive system is less than, or equal to approximately 2.7 N-m (2 ft-lb). In a further detailed embodiment, the accessory is an automotive water pump and the accessory pulley is operatively coupled to a shaft of the water pump. In a further detailed embodiment, the multiple-pulley accessory drive system is a two-pulley accessory drive system.
In an alternative detailed embodiment of the second aspect of the present invention, the endless drive belt has a tensile modulus of approximately 7,800 N/mm/mm (1750 lbf/in/in) to approximately 8,500 N/mm/mm (1910 lbf/in/in).
It is a third aspect of the present invention to provide a two-pulley accessory drive system for an automobile that includes: (a) a drive pulley; (b) an accessory pulley operatively coupled to accessory drive shaft; (c) an endless drive belt engaged between the drive pulley and the accessory pulley, where the drive belt includes an endless band of rubber composite material having a plurality of circumferentially extending and axially aligned cords formed therewithin; (d) where the endless drive belt has a tensile modulus of approximately 8500N/mm/mm (1910 lbf/in/in); and (e) where the circumferential length of the endless drive belt, before installation on the pulleys, is approximately 2.2% to approximately 2.3% lower than the nominal drive length between the drive pulley and the accessory pulley. In a further detailed embodiment the cords are polyamide 6.6 twisted cords.
A fourth aspect of the present invention is directed to a multiple-pulley system for an automobile that includes: (a) drive pulley; (b) an accessory pulley operatively coupled to an accessory drive shaft; and (c) a endless drive belt engaged between the drive pulley and the accessory pulley, where the drive belt includes an endless band of rubber composite material having a plurality of circumferentially extending and axially aligned, polyamide 6.6 twisted cords formed therewithin; (d) where the circumferential length of the endless drive belt, before installation on the pulleys is approximately 2.2% to approximately 2.3% lower than the nominal drive length of the accessory drive system. In a further detailed embodiment, the axial distance between the twisted cords is approximately 0.3 mm (0.012 in.) and each of the twisted cords includes a pair of cord yarns twisted together, where each cord has a diameter of approximately 0.58 mm (0.023 in.).
In an alternate detailed embodiment of the fourth aspect of the present invention, the operational torque of the accessory drive system is less than, or equal to approximately 2.7 N-m (2 ft-lbs). In a further detailed embodiment, the accessory is an automotive water pump and the accessory pulley is operatively coupled to a drive shaft of the water pump.
A fifth aspect of the present invention is directed to a method for fabricating an accessory drive belt that includes the steps of: (a) applying at least a layer of fabric or rubber material to an outer circumferential surface of a drum; (b) applying at least a first layer of cushion stock rubber material to the drum over the fabric layer; (c) winding a polyamide 6.6 twisted cord to the drum over the first layer of cushion stock; (d) applying a layer of relatively strong and wear resistant, fiber loaded, rubber material to the drum over the cords; (e) curing the multiple layers together into a cured sleeve of belt composite material; (f) cutting the cured sleeve into a plurality of endless belts; and (g) turning the endless belt inside-out for use as an accessory drive belt; (h) where the polyamide 6.6 twisted cord is wound in the winding step at approximately 3 lbf. (13 N) to approximately 3.5 lbf. (15.5 N). In a more detailed embodiment, the winding step axially spaces the winds of the polyamide 6.6 twisted cord at approximately 0.40 mm (26 cpi) to approximately 0.30 mm (30 cpi). In yet a further detailed embodiment the method further includes the step of, prior to the step of turning the endless belt inside out, forming a plurality of circumferential grooves into the outer circumferential surface of the cured sleeve or of the endless belts. In an alternate detailed embodiment to the fifth aspect of the present invention, the method includes, after the winding step (c) and before the applying step (d), the step of (c1) applying at least a second layer of the cushion stock over the cords.
A sixth aspect of the present invention is directed to an accessory drive belt for an automobile comprising a composite rubber and reinforcing cord composite, where the belt is adapted to be manually stretched on the pulleys of the accessory drive system and has an install tension; and where the belt maintains approximately at least 40% of its install tension throughout the useful life of the belt. In a detailed embodiment, the belt maintains at least approximately 40% to approximately 60% of its install tension throughout the useful life of the belt. In a further detailed embodiment, the cords in the composite are polyamide 6.6 twisted cords.